Lemon and Herb Roasted Chicken

1 roasting chicken, about 4 to 5 pounds
Juice of 1/2 lemon
Salt and pepper to taste
1 small onion, peeled and quartered
1 rib celery, cut into large chunks
Few sprigs fresh parsley
4 tablespoons melted butter
3 tablespoons coarsely chopped fresh parsley
1/4 teaspoon dried rosemary, crumbled
1/2 teaspoon dried leaf thyme